Referring to FIG. 1 of the drawings, the reference numeral 100 generally designates a typical configuration of a signal acquisition system. There are multiple channels or multiplexer inputs CH1 to CHx having or coupled to respective input pins S1 to Sx. A filter 102 to 108 is coupled to each of the channels CH1 to CHx for filtering the input signals, which are received through pins S1 through Sx. The filters 102 to 108 each pass relevant signals to the measurement channel MC, which includes an amplifier stage 312. The multiplexer or Mux 310 allows the same measurement channel to be used for multiple input signals by switching the respective input through to the multiplexer output OUT. Thereby, the same electronic components of the measurement channel MC can be used for each channel CH1 to CHx. This is typically accomplished by a differential amplifier 114, as shown in FIG. 1. In order to protect the amplifier 114 from dynamic and static overload condition a clamping stage 116 is present in almost all commercially available, e.g., high voltage, amplifiers. This clamping stage 116 is activated if a clamping condition occurs, e.g., if the output signal of the multiplexer changes suddenly from one input signal to another, suddenly placing a large and potentially damaging differential voltage across the amplifier differential inputs. However, the activation of the input clamp protection 116 draws a substantial amount of current from the filters 102 to 108. This current has to be compensated (e.g., by the signal source). This can cause a long settling of the voltage at multiplexer output OUT, which limits the system's settling time and the overall signal throughput. The situation is further illustrated in FIG. 2.
As shown in FIG. 2, the multiplexer output voltage OUT is switched from a first signal from channel CH1 to a second signal from channel CH2. The two signals have a large difference of potentials. This causes the input clamp protection 116 at the amplifier stage 112 to be activated. Therefore, a large current into the protection clamp 116 is drawn at the input of the measurement channel MC. This current is supplied by the input filter 104. The filter recharge rate and the settling time depend on the filter characteristic and architecture as well as on the input signal characteristics. Due to the filter's influence, the error from the ideal value, which is the difference between the ideal and the actual OUT becomes significant as shown in FIG. 2. In order to overcome these problems, prior art solutions, which are conceived to minimize the settling time, rely basically on using smaller filters. Other solutions use designated channels as reference channels, to which the multiplexer 110 switches between each change from a first channel CH1 to a second channel CH2 and vice-versa. This provides that the starting point for each measurement is known. However, use of a reference channel increases complexity of the switching and of the circuit as such.